PORTLAND, Ore. (AP) — A flight attendant found a .22-caliber bullet on the floor Friday as passengers were boarding a Southwest Airlines plane headed from Portland to Chicago, delaying the flight nearly two hours.

A Port of Portland spokesman, Steve Johnson, says passengers were taken off the plane to be re-screened, and the plane was searched. He says all were cleared for the flight to take off. The port operates the Portland International Airport.

Johnson says the port is still looking into how the bullet got on the aircraft. A report from the port police agency said it was found near the front of the plane.

The bullet was found at about 6:15 a.m. on a flight with a scheduled 6:30 takeoff. The airline’s website says it departed at 8:14 a.m.